It is known to use a suction force to operate a device between two states. For instance, in U.S. Pat. No. 5,099,544, an electric switch is closed when suction is present and this switch opens when the suction is discontinued.
It is desirable to provide a system in which a part is continuously moved in a reciprocating movement under the action of a suction source.
In a known type of central vacuum cleaning apparatus, the dust conveyed by the suction lines is discharged by a cyclone device into a dust collecting tank: heavier dust particles settle in the bottom of the tank whereas the finer dust particles accumulate against a filter; the filtered air can be discharged within the building. However, frequent cleaning of the filter is required to prevent decrease of the cleaning efficiency of the apparatus. Filter cleaning is usually effected manually, however there exists an automatic filter cleaning device which consists of a weight secured to the lower end of the filter which is conical in shape. The filter and weight moves up when suction is applied and upon stoppage of the cleaning apparatus, the weight drops down thereby shaking the filter to remove the dust adhering thereto. Tests have shown that this system can be improved upon since dust removal has been found rather inefficient because filter shaking occurs only when the apparatus is turned off and often the weight drops too slowly.